Cartilage is a type of firm, thick, slippery tissue that coats the ends of bones where they meet with other bones to form a joint. Cartilage acts as a protective cushion between bones. In the knee, there is cartilage on the ends of the bones and at the back of the kneecap (patella).

A meniscus is a piece of cartilage that acts as a shock absorber between bones. It stabilizes the joints by evenly distributing the load across the joint area. In the knee, the crescent-shaped menisci are in between the ends of the upper (femur) and lower (tibia) leg bones. The menisci protect the knee joint surface and absorb the shock produced by activities such as walking, running, and jumping.